Why is my back face culling reversed?

The front is invisible and the back faces are solid. I tried to paste a screenshot directly to this post but it gives me a 'bad request' error on posting so it's here as a link https://app.screencast.com/UvIhzM0mfrUaa

  • Martin Bergwerf replied

    That is because your Normals are flipped. In edit Mode, select all (A) and then SHIFT+N, to recalculate the Normals.

  • Martin Bergwerf replied

    So, the invisible front is actually the back of a Face...


  • Martin Bergwerf replied

    You can also use the Face Orientation Overlay to check your Normals (Red is the back of a Face):

    Normal.png

    So: "red is bad and blue is good".

  • thehomme replied

    OK thanks. This makes sense. If you extrude +z then normals are fine but if you extrude in -z (as in the video) you get reversed normals. 

    So why doesn't the teacher have the same problem? Was there an edit?

  • Martin Bergwerf replied

    It depends on the Orientation of what you are Extruding.

  • Martin Bergwerf replied


    Extruding.png

  • thehomme replied

    Hmmm ok. I've tried to replicate with a new circle and extruding down -z and all the new ones now output normal outward facing normals. The only way I've been able to get red normals on the outside by extruding down on the -z is to flip the circle. It's a gotcha for me as this just doesn't happen in C4D. You can find normals reversed but it only really happens as a result of detailed mesh editing and joining edges between separate models

  • Dwayne Savage(dillenbata3) replied

    That's because C4D is designed with 3D motion graphics as it's main focus. Blender is designed with 3D animation as it's main focus. There are several uses for having normals inside instead of outside. For example inverted hull method uses to create outline for NPR animation.